1. Field of the Invention
The present invention relates to a process for forming a deposition film, particularly to a process for forming an aluminum deposition film suitably used for wiring in semiconductor integrated circuit devices and the like.
2. Related Background Art
In semiconductor electronic devices and semiconductor integrated circuits of the prior art, aluminum (Al) or aluminum-silicon and the like are mainly used as electrodes and wiring materials. Aluminum is advantageous in various points such that it is inexpensive yet has high electroconductivity; its interior is protected and stabilized by a fine oxide film formed on the surface; it has sufficient adhesiveness to silicon; and so forth.
With the recent trend of raising the integration degree of integration circuits such as LSI, finer wiring and multiple-layer wiring are needed, and more severe conditions than ever has come to be required in aluminum wiring. As the result of increase of fineness of the integrated circuit by 1 increase of the integration degree, the surface of LSI or the like is made highly toughened by oxidation, diffusion, thin film deposition, etching, or the like treatment. Therefore, an electrode material or a wiring material has to be deposited on a stepped face without disconnection, or deposited in a deep via hole having a minute diameter. In DRAM (dynamic RAM) of 4 Mbit or 16 Mbit, or the like, the via hole in which a metal such as aluminum is to be deposited has an aspect ratio (via hole depth divided by via hole diameter) is not less than 1.0 and a diameter of the via hole is not larger than 1 .mu.m. Accordingly, technique is needed for depositing aluminum in a via hole having a high aspect ratio. The aluminum, which is used to fill a via hole, is also to be deposited for wiring in extremely high quality on a insulating film.
Recently, the inventors of the present invention, et al. have proposed the use of dimethylaluminum hydride in a chemical vapor deposition (CVD) process as a technique for forming an aluminum film. Although this process is promising for ultra-fine processing in the semiconductor manufacturing technique, further improvement thereof is desired for raising the yield of production of semiconductor devices to lower the price and to achieve success in commercialization.
The inventors of the present invention have found that the variation in film formation, particularly in an early stage of aluminum deposition, seems to affect the final product yield. The inventors have further found that the variation of properties at the interface between a selectively deposited aluminum film end a non-selectively deposited aluminum film possibly affects the final product yield on basis of the hypothesis of deposition mechanism described later.